Video Editing (NLE): Time results of rendering in non-native resolution
Blender's VSE always scales the image, unless the source is the same size as project.

The project's render properties determine the speed of the scale process.
In the properties panel look for Anti-Aliasing.



For best speed of scale turn this off. However the image will have jagged edges.



To improve quality of the VSE scaling or other transform effects, you must turn on the Anti-aliasing. There are many levels and algorithms to choose from. The render-speed change may not seem to great, but you must multiply the difference out over the total number of frames rendered. And this example was based on a very simple image.